U.S. patent application number 15/424569 was filed with the patent office on 2018-08-09 for mobility-aware contention procedures on a shared communication medium.
The applicant listed for this patent is QUALCOMM Incorporated. Invention is credited to Farhad MESHKATI, Chirag Sureshbhai PATEL, Rajat PRAKASH, Damanjit SINGH.
Application Number | 20180227954 15/424569 |
Document ID | / |
Family ID | 60888658 |
Filed Date | 2018-08-09 |
United States Patent
Application |
20180227954 |
Kind Code |
A1 |
SINGH; Damanjit ; et
al. |
August 9, 2018 |
MOBILITY-AWARE CONTENTION PROCEDURES ON A SHARED COMMUNICATION
MEDIUM
Abstract
Techniques for mobility-aware contention procedures on a shared
communication medium are disclosed. A connection failure associated
with mobility between a source access point and a target access
point sharing a communication medium may be detected. Based on the
detected connection failure, a backoff threshold associated with
contention-based access to the communication medium may be adapted.
Contention for access to the communication medium may then proceed
in accordance with the adapted backoff threshold.
Inventors: |
SINGH; Damanjit; (San Diego,
CA) ; PATEL; Chirag Sureshbhai; (San Diego, CA)
; PRAKASH; Rajat; (San Diego, CA) ; MESHKATI;
Farhad; (San Diego, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
|
Family ID: |
60888658 |
Appl. No.: |
15/424569 |
Filed: |
February 3, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 36/08 20130101;
H04W 76/18 20180201; H04W 74/0816 20130101; H04W 16/16
20130101 |
International
Class: |
H04W 74/08 20060101
H04W074/08; H04W 76/02 20060101 H04W076/02 |
Claims
1. A communication method, comprising: detecting a connection
failure associated with mobility between a source access point and
a target access point sharing a communication medium; adapting,
based on the detected connection failure, a backoff threshold
associated with contention-based access to the communication
medium; and contending for access to the communication medium in
accordance with the adapted backoff threshold.
2. The method of claim 1, further comprising adapting, based on the
detected connection failure, one or more handover parameters
distinct from the backoff threshold.
3. The method of claim 1, wherein the adapting comprises lowering
the backoff threshold from a first value to a second value in
response to detecting the connection failure.
4. The method of claim 1, wherein the detecting utilizes
communication between the source access point and the target access
point.
5. The method of claim 4, wherein the detecting further utilizes
Mobility Robustness Optimization (MRO) procedures.
6. The method of claim 1, wherein the detecting utilizes
communication between the access terminal and the source access
point, communication between the access terminal and the target
access point, or a combination thereof.
7. The method of claim 1, further comprising coordinating the
adapted backoff threshold between the source access point and the
target access point, via a backhaul connection, an over-the-air
connection, or an access terminal report.
8. The method of claim 1, wherein: the detecting comprises
classifying the detected connection failure; and the adapting
comprises selectively adapting the backoff threshold based on the
classifying.
9. The method of claim 1, wherein the adapting comprises switching
a Listen Before Talk (LBT) mode from a first detection mechanism
having a first backoff threshold to a second detection mechanism
having a second backoff threshold that is lower than the first
backoff threshold.
10. The method of claim 9, wherein the first detection mechanism
corresponds to a Clear Channel Assessment (CCA) Energy Detection
(CCA-ED) mechanism and the second detection mechanism corresponds
to a CCA Preamble Detection (CCA-PD) mechanism.
11. The method of claim 1, wherein the backoff threshold is a Radio
Access Technology (RAT)-specific threshold and wherein the adapting
comprises setting a first backoff threshold associated with a first
RAT to a first value and a second backoff threshold associated with
a second RAT to a second value that is different from the first
value.
12. The method of claim 1, wherein the backoff threshold is a Cell
Identifier (Cell ID)-specific threshold and wherein the adapting
comprises setting a first backoff threshold associated with a first
Cell ID to a first value and a second backoff threshold associated
with a second Cell ID to a second value that is different from the
first value.
13. The method of claim 1, wherein the connection failure
corresponds to a Radio Link Failure (RLF) or a handover
failure.
14. A communication apparatus, comprising: at least one processor;
at least one memory coupled to the at least one processor, the at
least one processor and the at least one memory being configured
to: detect a connection failure associated with mobility between a
source access point and a target access point sharing a
communication medium, adapt, based on the detected connection
failure, a backoff threshold associated with contention-based
access to the communication medium; and at least one transceiver
configured to contend for access to the communication medium in
accordance with the adapted backoff threshold.
15. The apparatus of claim 14, wherein the at least one processor
and the at least one memory are further configured to adapt, based
on the detected connection failure, one or more handover parameters
distinct from the backoff threshold.
16. The apparatus of claim 14, wherein the at least one processor
and the at least one memory are configured to adapt the backoff
threshold by lowering the backoff threshold from a first value to a
second value in response to detecting the connection failure.
17. The apparatus of claim 14, wherein the at least one processor
and the at least one memory are configured to detect the connection
failure by utilizing communication between the source access point
and the target access point.
18. The apparatus of claim 17, wherein the at least one processor
and the at least one memory are configured to detect the connection
failure by further utilizing Mobility Robustness Optimization (MRO)
procedures.
19. The apparatus of claim 14, wherein the at least one processor
and the at least one memory are configured to detect the connection
failure by utilizing communication between the access terminal and
the source access point, communication between the access terminal
and the target access point, or a combination thereof.
20. The apparatus of claim 14, wherein the at least one transceiver
is further configured to coordinate the adapted backoff threshold
between the source access point and the target access point, via a
backhaul connection, an over-the-air connection, or an access
terminal report.
21. The apparatus of claim 14, wherein the at least one processor
and the at least one memory are further configured to: classify the
detected connection failure; and selectively adapt the backoff
threshold based on the classifying.
22. The apparatus of claim 14, wherein the at least one processor
and the at least one memory are configured to adapt the backoff
threshold by switching a Listen Before Talk (LBT) mode from a first
detection mechanism having a first backoff threshold to a second
detection mechanism having a second backoff threshold that is lower
than the first backoff threshold.
23. The apparatus of claim 22, wherein the first detection
mechanism corresponds to a Clear Channel Assessment (CCA) Energy
Detection (CCA-ED) mechanism and the second detection mechanism
corresponds to a CCA Preamble Detection (CCA-PD) mechanism.
24. The apparatus of claim 14, wherein the backoff threshold is a
Radio Access Technology (RAT)-specific threshold and wherein the at
least one processor and the at least one memory are configured to
adapt the backoff threshold by setting a first backoff threshold
associated with a first RAT to a first value and a second backoff
threshold associated with a second RAT to a second value that is
different from the first value.
25. The apparatus of claim 14, wherein the backoff threshold is a
Cell Identifier (Cell ID)-specific threshold and wherein the at
least one processor and the at least one memory are configured to
adapt the backoff threshold by setting a first backoff threshold
associated with a first Cell ID to a first value and a second
backoff threshold associated with a second Cell ID to a second
value that is different from the first value.
26. The apparatus of claim 14, wherein the connection failure
corresponds to a Radio Link Failure (RLF) or a handover
failure.
27. A communication apparatus, comprising: means for detecting a
connection failure associated with mobility between a source access
point and a target access point sharing a communication medium;
means for adapting, based on the detected connection failure, a
backoff threshold associated with contention-based access to the
communication medium; and means for contending for access to the
communication medium in accordance with the adapted backoff
threshold.
28. The apparatus of claim 27, wherein the means for adapting
comprises means for lowering the backoff threshold from a first
value to a second value in response to detecting the connection
failure.
29. A non-transitory computer-readable medium comprising code,
which, when executed by at least one processor, causes the at least
one processor to perform operations for communication, the
non-transitory computer-readable medium comprising: code for
detecting a connection failure associated with mobility between a
source access point and a target access point sharing a
communication medium; code for adapting, based on the detected
connection failure, a backoff threshold associated with
contention-based access to the communication medium; and code for
contending for access to the communication medium in accordance
with the adapted backoff threshold.
30. The non-transitory computer-readable medium of claim 29,
wherein the code for adapting comprises code for lowering the
backoff threshold from a first value to a second value in response
to detecting the connection failure.
Description
BACKGROUND
[0001] Aspects of this disclosure relate generally to
telecommunications, and more particularly to operations on a shared
communication medium and the like.
[0002] Wireless communication systems are widely deployed to
provide various types of communication content, such as voice,
data, multimedia, and so on. Typical wireless communication systems
are multiple-access systems capable of supporting communication
with multiple users by sharing available system resources (e.g.,
bandwidth, transmit power, etc.). Examples of such multiple-access
systems include Code Division Multiple Access (CDMA) systems, Time
Division Multiple Access (TDMA) systems, Frequency Division
Multiple Access (FDMA) systems, Orthogonal Frequency Division
Multiple Access (OFDMA) systems, and others. These systems are
often deployed in conformity with specifications such as 5.sup.th
Generation (5G)/New Radio (NR), Long Term Evolution (LTE) provided
by the Third Generation Partnership Project (3GPP), Ultra Mobile
Broadband (UMB) and Evolution Data Optimized (EV-DO) provided by
the Third Generation Partnership Project 2 (3GPP2), 802.11 provided
by the Institute of Electrical and Electronics Engineers (IEEE),
etc.
[0003] In cellular networks, "macro cell" access points provide
connectivity and coverage to a large number of users over a certain
geographical area. A macro network deployment is carefully planned,
designed, and implemented to offer good coverage over the
geographical region. To improve indoor or other specific geographic
coverage, such as for residential homes and office buildings,
additional "small cell," typically low-power access points have
recently begun to be deployed to supplement conventional macro
networks. Small cell access points may also provide incremental
capacity growth, richer user experience, and so on.
[0004] Small cell operations have been extended into so-called
"unlicensed" and "lightly licensed" frequency spectra, for example,
such as the Unlicensed National Information Infrastructure (U-NII)
band and the Citizens Broadband (CB) Radio Service band. This
extension of small cell operation is designed to increase spectral
efficiency and hence overall system capacity. However, it may also
lead to varying degrees of interference between small cell access
points and operators as their devices compete for access to shared
resources.
SUMMARY
[0005] The following summary is an overview provided solely to aid
in the description of various aspects of the disclosure and is
provided solely for illustration of the aspects and not limitation
thereof.
[0006] In one example, a communication method is disclosed. The
method may include, for example, detecting a connection failure
associated with mobility between a source access point and a target
access point sharing a communication medium; adapting, based on the
detected connection failure, a backoff threshold associated with
contention-based access to the communication medium; and contending
for access to the communication medium in accordance with the
adapted backoff threshold.
[0007] In another example, a communication apparatus is disclosed.
The apparatus may include, for example, at least one processor, at
least one memory coupled to the at least one processor, and at
least one transceiver. The at least one processor and the at least
one memory may be configured to detect a connection failure
associated with mobility between a source access point and a target
access point sharing a communication medium and to adapt, based on
the detected connection failure, a backoff threshold associated
with contention-based access to the communication medium. The at
least one transceiver may be configured to contend for access to
the communication medium in accordance with the adapted backoff
threshold.
[0008] In another example, another communication apparatus is
disclosed. The apparatus may include, for example, means for
detecting a connection failure associated with mobility between a
source access point and a target access point sharing a
communication medium; means for adapting, based on the detected
connection failure, a backoff threshold associated with
contention-based access to the communication medium; and means for
contending for access to the communication medium in accordance
with the adapted backoff threshold.
[0009] In another example, a transitory or non-transitory
computer-readable medium is disclosed, which, when executed by at
least one processor, causes the at least one processor to perform
operations for communication. The computer-readable medium may
include, for example, code for detecting a connection failure
associated with mobility between a source access point and a target
access point sharing a communication medium; code for adapting,
based on the detected connection failure, a backoff threshold
associated with contention-based access to the communication
medium; and code for contending for access to the communication
medium in accordance with the adapted backoff threshold.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The accompanying drawings are presented to aid in the
description of various aspects of the disclosure and are provided
solely for illustration of the aspects and not limitation
thereof.
[0011] FIG. 1 is a system-level diagram illustrating an example
wireless network environment.
[0012] FIG. 2 illustrates an example of inter-access point mobility
and connection failure scenarios.
[0013] FIG. 3 is a signaling flow diagram illustrating example
aspects of mobility-aware contention.
[0014] FIG. 4 illustrates an example of inter-access point
coordination with respect to backoff thresholds.
[0015] FIG. 5 is a flow chart illustrating an example of
classification-based backoff threshold adaption.
[0016] FIG. 6 illustrates an example of Listen Before Talk
(LBT)-mode switching to effectuate the adaption of the backoff
threshold(s).
[0017] FIG. 7 illustrates an example of RAT-specific backoff
threshold(s) settings.
[0018] FIG. 8 illustrates an example of Cell Identifier (Cell
ID)-specific backoff threshold(s) settings.
[0019] FIG. 9 is a flow diagram illustrating an example method of
communication in accordance with the techniques described
herein.
[0020] FIG. 10 is a device-level diagram illustrating example
components of an access point and an access terminal in more
detail.
[0021] FIG. 11 illustrates an example apparatus represented as a
series of interrelated functional modules.
DETAILED DESCRIPTION
[0022] The present disclosure relates generally to mobility-aware
contention procedures on a shared communication medium. To improve
mobility performance when contention-based access is employed on
the communication medium (including both connected-mode mobility,
which may be referred to as handover, and idle-mode mobility), one
or more backoff thresholds that determine how deferential systems
are to one another in contending for access to the communication
medium can be adapted based on the detection of a connection
failure. For example, a serving access point and a target access
point may agree to lower the backoff threshold they use with
respect to each other in response to detecting that a connection
failure has occurred between them. A more deferential backoff
threshold may help to prevent or reduce simultaneous transmission,
thus effectively increasing the transition region and associated
time for completing transition from one access point to the other.
This approach may be used in addition or as an alternative to
adapting other, mobility-related parameters, as well as selectively
for different types of connection failures (e.g., those based on
interference-related failures rather than coverage holes). The
access points involved may coordinate their backoff thresholds to
maintain fairness, and implement different thresholds in different
ways (e.g., using preamble detection as opposed to energy detection
mechanisms). Different thresholds may also be used for different
groups of entities (e.g., those associated with a particular Radio
Access Technology (RAT)) or different specific entities (e.g.,
those associated with a particular Cell Identifier (Cell ID)).
[0023] More specific aspects of the disclosure are provided in the
following description and related drawings directed to various
examples provided for illustration purposes. Alternate aspects may
be devised without departing from the scope of the disclosure.
Additionally, well-known aspects of the disclosure may not be
described in detail or may be omitted so as not to obscure more
relevant details.
[0024] Those of skill in the art will appreciate that the
information and signals described below may be represented using
any of a variety of different technologies and techniques. For
example, data, instructions, commands, information, signals, bits,
symbols, and chips that may be referenced throughout the
description below may be represented by voltages, currents,
electromagnetic waves, magnetic fields or particles, optical fields
or particles, or any combination thereof, depending in part on the
particular application, in part on the desired design, in part on
the corresponding technology, etc.
[0025] Further, many aspects are described in terms of sequences of
actions to be performed by, for example, elements of a computing
device. It will be recognized that various actions described herein
can be performed by specific circuits (e.g., Application Specific
Integrated Circuits (ASICs)), by program instructions being
executed by one or more processors, or by a combination of both. In
addition, for each of the aspects described herein, the
corresponding form of any such aspect may be implemented as, for
example, "logic configured to" perform the described action.
[0026] FIG. 1 is a system-level diagram illustrating an example
wireless network environment, shown by way of example as including
two systems, a first system A 100 and a second system B 150. Each
system may be composed of different wireless nodes generally
capable of receiving and/or transmitting over a wireless link,
including information related to various types of communication
(e.g., voice, data, multimedia services, associated control
signaling, etc.). The first system A 100 is shown as including an
access point 110 and an access terminal 120 in communication with
each other over a wireless link 130. The second system B 150 is
shown as including its own access point 160 and access terminal 170
in communication with each other over a separate wireless link 132.
In some deployments, the two systems may communicate with other via
a backhaul connection 180 (e.g., a so-called "X2" interface),
either with or without an intermediary such as an (optional)
central coordination server 182 or the like.
[0027] In general, the two systems may be deployed by the same or
by different operators (e.g., a common or distinct company or other
entity controlling authorization, system timing, etc.) and utilize
the same or different access technologies. As an example, the
access point 110 and the access terminal 120 of the first system A
100 may communicate via the wireless link 130 in accordance with a
Long Term Evolution (LTE) technology or a variant thereof (e.g.,
MuLTEfire, Licensed Assisted Access (LAA), etc.), while the access
point 160 and the access terminal 170 of the second system B 150
may communicate via the wireless link 132 in accordance with the
same LTE technology or a different technology (e.g., Wi-Fi
technology). It will be appreciated that each system may support
any number of wireless nodes (access points, access terminals,
etc.) distributed throughout a geographic region, with the
illustrated entities being shown for illustration purposes only.
Instead of LTE technology, persons skilled in the art will
appreciate that communications via wireless links 130 and 132 may
be configured in accordance with a fifth generation (5G)/new radio
(NR) technology or a variant thereof, among others.
[0028] Unless otherwise noted, the terms "access terminal" and
"access point" are not intended to be specific or limited to any
particular Radio Access Technology (RAT). In general, access
terminals may be any wireless communication device allowing a user
to communicate over a communications network (e.g., a mobile phone,
router, personal computer, server, entertainment device, Internet
of Things (IOT)/Internet of Everything (IOE) capable device,
in-vehicle communication device, etc.), and may be alternatively
referred to in different RAT environments as a User Device (UD), a
Mobile Station (MS), a Subscriber Station (STA), a User Equipment
(UE), etc. Similarly, an access point may operate according to one
or several RATs in communicating with access terminals depending on
the network in which the access point is deployed, and may be
alternatively referred to as a Base Station (BS), a Network Node, a
NodeB, an evolved NodeB (eNB), etc. Such an access point may
correspond to a small cell access point, for example. "Small cells"
generally refer to a class of low-powered access points that may
include or be otherwise referred to as femto cells, pico cells,
micro cells, Wireless Local Area Network (WLAN) access points,
other small coverage area access points, etc. Small cells may be
deployed to supplement macro cell coverage, which may cover a few
blocks within a neighborhood or several square miles in a rural
environment, thereby leading to improved signaling, incremental
capacity growth, richer user experience, and so on.
[0029] Returning to FIG. 1, the wireless link 130 used by the first
system A 100 and the wireless link 132 used by the second system B
150 may operate over a shared communication medium 140. A
communication medium of this type may be composed of one or more
frequency, time, and/or space communication resources (e.g.,
encompassing one or more channels across one or more carriers). As
an example, the communication medium 140 may correspond to at least
a portion of an unlicensed or lightly licensed frequency band.
Although different licensed frequency bands have been reserved for
certain communications (e.g., by a government entity such as the
Federal Communications Commission (FCC) in the United States), some
systems, in particular those employing small cell access points,
have extended operation into unlicensed and lightly licensed
frequency bands such as the Unlicensed National Information
Infrastructure (U-NII) band and the Citizens Broadband (CB) Radio
Service band.
[0030] Due to the shared use of the communication medium 140, there
is the potential for cross-link interference between the wireless
link 130 and the wireless link 132. Further, some RATs and some
jurisdictions may require contention or "Listen Before Talk (LBT)"
for arbitrating access to the communication medium 140. As an
example, a Clear Channel Assessment (CCA) protocol may be used in
which each device verifies via medium sensing the absence of other
traffic on a shared communication medium before seizing (and in
some cases reserving) the communication medium for its own
transmissions. In some designs, the CCA protocol may include
distinct CCA Preamble Detection (CCA-PD) and CCA Energy Detection
(CCA-ED) mechanisms utilizing different backoff thresholds for
yielding the communication medium to intra-RAT and inter-RAT
traffic, respectively. The European Telecommunications Standards
Institute (ETSI), for example, mandates contention for all devices
regardless of their RAT on certain communication media such as
unlicensed frequency bands.
[0031] FIG. 2 illustrates an example of inter-access point mobility
and connection failure scenarios. In this example, the access point
110 (AP-1) of the first system A 100 is shown as being deployed in
the vicinity of the access point 160 (AP-2) of the second system B
150. Each of the access points 110 and 160 provides communication
services over respective coverage areas 202 and 204 to their
respective access terminals, shown by way of example as the access
terminal 120 (AT-1) and the access terminal 170 (AT-2). Because of
the overlap between the two coverage areas 202 and 204, the access
terminal 120, for example, may, under certain conditions or
scenarios, attempt a transition from the access point 110 to the
access point 160, with the access point 110 acting as the "source"
access point for the transition procedure and the access point 160
acting as the "target" access point for the transition procedure
(including both connected-mode mobility procedures, which may be
referred to as handover, and idle-mode mobility procedures).
[0032] Connection failures such as Radio Link Failure (RLF) and
handover failure may occur for various reasons and be detected in
different ways, including using communication between the serving
access point 110 and the target access point 160 or between the
access terminal 120 and the serving access point 110 and/or the
target access point 160. For example, the serving access point 110
and/or the target access point 160 may detect connection failures
using Mobility Robustness Optimization (MRO) procedures or the
like. MRO is defined in 3GPP TS 36.300 Release 9 and onward, and
includes procedures for detecting and classifying connection
failures as "too late handover," "too early handover," and
"handover to wrong cell."
[0033] Two example connection failures are illustrated in FIG. 2,
including a so-called "too late" handover failure and a "too early"
handover failure. Handovers, for example, that are "too late" are
connection failures that may occur at the serving access point 110
before a handover is initiated or during the handover, prompting
the access terminal 120 to initiate a re-establishment procedure to
re-establish a radio link connection at the target access point
160. This may occur, for example, if the access terminal 120 is
moving more quickly than a corresponding handover policy can
accommodate. Handovers that are "too early" are connection failures
that may occur shortly after a successful handover or during a
handover of the access terminal 120 to the target access point 160,
prompting the access terminal 120 to initiate a re-establishment
procedure to re-establish a radio link connection with the serving
access point 110. This may occur, for example, when the access
terminal 120 enters and quickly exits a small, island coverage
region of the target access point 160. Other example connection
failures include "wrong cell" handover where the access terminal
120 attempts to transition to a different access point.
[0034] Connection failure can be conventionally addressed to some
degree by changing different mobility-specific parameters for the
serving access point 110 and/or the target access point 160 (e.g.,
a signal quality offset parameter, a hysteresis parameter, an event
offset parameter such as a3-offset, a cell individual offset
parameter, a reporting range parameter, a frequency offset
parameter, a time-to-trigger parameter, etc.). For example, if a
delay in transitioning to the target access point 160 causes a
connection failure, a corresponding parameter can be changed to
allow earlier mobility. However, this approach may be insufficient
or at least sub-optimal when contention-based access is employed on
the communication medium 140.
[0035] To improve mobility performance, the access point 110 and/or
the access point 160 may be configured for mobility-aware
contention procedures for accessing the communication medium 140.
For example, the access point 110 may include a contention manager
112 and the access point 160 may include a contention manager 162,
as shown in FIG. 1. The contention manager 112 and/or the
contention manager 162 may be configured in different ways to
manage contention-based access to the communication medium 140
based on any detected connection failures.
[0036] FIG. 3 is a signaling flow diagram illustrating example
aspects of mobility-aware contention. It will be appreciated that
the illustrated signaling is a generalization shown only in
relevant part, and that certain illustrated signaling may be
omitted while other signaling may be added for a given mobility or
contention procedure implementation.
[0037] Continuing with the example deployment scenario of FIG. 2,
the access terminal 120 in FIG. 3 initially operates in an idle or
connected state with the serving access point 110 (e.g., a Radio
Resource Control (RRC) connection or the like) in the vicinity of
the target access point 160. At some point, a transition is
initiated for the access terminal 120 and corresponding mobility
signaling 310 is exchanged. The serving access point 110 and/or the
target access point 160 may monitor the mobility signaling 310 as
well as any other relevant information to detect whether a
connection failure has occurred (block 312). As discussed above,
connection failures such as handover failure and RLF may occur for
various reasons and be detected in different ways, including via
MRO procedures and the like, or other connection failure detection
and classification techniques as may be available or appropriate
for different applications and different RATs.
[0038] Based on the detected connection failure, the serving access
point 110 and/or the target access point 160 may adapt one or more
backoff thresholds associated with contention-based access to the
communication medium 140 (block 314) and contend for access to the
communication medium 140 in accordance with the adapted backoff
threshold (respective blocks 316 and 318). By adapting a backoff
threshold in addition or as an alternative to any distinct mobility
parameter adaptation, the interference between the serving access
point 110 and the target access point 160 at any given time can be
minimized or at least reduced. For example, the serving access
point 110 may lower the backoff threshold it uses with respect to
the target access point 160 from a first value to a second value in
response to detecting the connection failure in order to increase
the likelihood that the serving access point 110 will yield the
communication medium 140 to the target access point 160. Yielding
the communication medium 140, in turn, reduces the interference
perceived by the access terminal 120 at the boundary between the
coverage areas 202 and 204, thereby reducing the interference
portion of the perceived Signal-to-Interference-plus-Noise (SINR)
ratio that is used to determine various aspects related to mobility
(e.g., when and how soon a transition is desirable, etc.). Put
another way, a more deferential backoff threshold may help to
prevent or reduce simultaneous transmission by the serving access
point 110 and the target access point 160, thus effectively
increasing the transition region and associated time.
[0039] FIG. 4 illustrates an example of inter-access point
coordination with respect to backoff thresholds. In this example,
the serving access point 110 and the target access point 160 have
access to the shared backhaul connection 180 (e.g., X2 interface)
and respective wireless links 130 and 132 with the access terminal
120.
[0040] In some networks, the adapted backoff threshold(s) may be
coordinated between the source access point 110 and the target
access point 160. Coordination may help to maintain fairness
between the first system A 100 and the second system B 150.
Otherwise, a disparity may arise between their respective backoff
thresholds, such that one system would yield the communication
medium 140 to the other less often, leading to a corresponding
disparity in medium access.
[0041] As an example, the source access point 110 and the target
access point 160 may exchange a backoff threshold parameter(s)
message 402 over the backhaul connection 180, or via an
over-the-air connection between the two, if available. The backoff
threshold parameter(s) message 402 may indicate to the receiving
entity that one or more backoff thresholds have been set to a given
level and request that the receiving entity do the same or similar.
As another example, the source access point 110 and/or the target
access point 160 may receive an access terminal report 404 from the
access terminal 120 over the respective wireless links 130 and 132
(e.g., as part of a mobility message to the target access point
160, a measurement report to the source access point 110, etc.).
The access terminal report 404 may indicate to the receiving entity
that one or more backoff thresholds have been set to a given level
and prompt the receiving entity do the same or similar.
[0042] FIG. 5 is a flow chart illustrating an example of
classification-based backoff threshold adaption. The illustrated
diagram shows additional aspects that may be implemented as part of
the detecting (block 312) and the adapting (block 314) of FIG.
3.
[0043] In some designs, the source access point 110 and/or the
target access point 160 may selectively adapt the backoff
threshold(s) based on the type of connection failure that is
detected. As an example, the source access point 110 and/or the
target access point 160 may adapt the backoff threshold(s) when it
is determined that the connection failure is an interference-type
of failure (e.g., a "too late" or "too early" type failure), but
not when it is determined that the connection failure is due to
some other cause (e.g., a "wrong cell" type of failure). Based on
the respective signal strengths reported by the access terminal 120
in its RLF report, for example, it may be determined that both the
source access point 110 and the target access point 160 have low
signal strength values--indicating a coverage hole--as opposed to a
high signal strength of the target access point 160 and a low
signal strength of the source access point 110, which would
indicate an interference-type of failure. Connection failures due
to coverage holes are unlikely to be helped by a more deferential
backoff threshold, which would therefore simply reduce medium
access and overall network capacity.
[0044] In the illustrated example of FIG. 5, the source access
point 110 and/or the target access point 160 may first classify the
detected connection failure (block 502). If the classification
indicates an interference-type failure (yes' at decision 504), the
backoff threshold(s) may be modified (block 506). Otherwise, if the
classification indicates another type of failure (`no` at decision
504), the backoff threshold(s) may not be modified (block 508).
[0045] FIG. 6 illustrates an example of LBT-mode switching to
effectuate the adaption of the backoff threshold(s). In this
example, the serving access point 110 and the target access point
160 are shown again in their respective coverage areas 202 and
204.
[0046] In some designs, the source access point 110 and/or the
target access point 160 may effectuate the adaption of the backoff
threshold(s) by switching an LBT mode from a first detection
mechanism having a first backoff threshold to a second detection
mechanism having a second backoff threshold that is lower than the
first backoff threshold. As discussed above, distinct CCA-ED and
CCA-PD mechanisms, for example, may utilize different backoff
thresholds for yielding the communication medium 140 to different
types of systems (e.g., to inter-RAT and intra-RAT traffic,
respectively). By agreeing to use a CCA-PD mechanism as opposed to
CCA-ED mechanism, the source access point 110 and the target access
point 160 can implement the correspondingly lower backoff threshold
and thereby treat each other more deferentially during
contention.
[0047] In the illustrated example of FIG. 6, the source access
point 110 and/or the target access point 160 may switch their
respective LBT settings 612 and 662, in response to a connection
failure between the two entities, from a respective CCA-ED setting
614 and 664 having a first threshold (TH.sub.1) to a respective
CCA-PD setting 616 and 666 having a second threshold
(TH.sub.2).
[0048] FIG. 7 illustrates an example of RAT-specific backoff
threshold(s) settings. In this example, the serving access point
110 and the target access point 160 are shown again in their
respective coverage areas 202 and 204.
[0049] In some designs, the source access point 110 and/or the
target access point 160 may maintain RAT-specific backoff
thresholds and set them to different values for different RATs. For
example, if a particular RAT has been determined to be interfering
and leading to increased connection failures, a CCA-PD mechanism
having a lower backoff threshold may be used for yielding the
communication medium 140 to entities associated with that RAT, as
opposed to a CCA-ED mechanism used for other RATs.
[0050] In the illustrated example of FIG. 7, the source access
point 110 and/or the target access point 160 may set their backoff
threshold(s) settings 712 and 762, in response to a connection
failure between the two entities, to a respective RAT-1 setting 714
and 764 having a first threshold (TH.sub.1) or to a respective
RAT-2 setting 716 and 766 having a second threshold (TH.sub.2).
[0051] FIG. 8 illustrates an example of Cell Identifier (Cell
ID)-specific backoff threshold(s) settings. In this example, the
serving access point 110 and the target access point 160 are shown
again in their respective coverage areas 202 and 204.
[0052] In some designs, the source access point 110 and/or the
target access point 160 may maintain further-refined
Cell-ID-specific backoff thresholds and set them to different
values for different Cell IDs (e.g., Physical Cell ID (PCI)). For
example, if a particular access point has been determined to be
interfering and leading to increased connection failures (e.g., a
cell with a signal strength that ramps up quickly, such as one
encountered in an urban environment when a typical user may turn a
corner), a CCA-PD mechanism having a lower backoff threshold may be
used for yielding the communication medium 140 to that entity in
particular, as opposed to a CCA-ED mechanism used for other Cell
IDs.
[0053] In the illustrated example of FIG. 8, the source access
point 110 and/or the target access point 160 may set their backoff
threshold(s) settings 812 and 862, in response to a connection
failure between the two entities, to a respective Cell-ID-1 setting
814 and 864 having a first threshold (TH.sub.1) or to a respective
Cell-ID-2 setting 816 and 866 having a second threshold
(TH.sub.2).
[0054] FIG. 9 is a flow diagram illustrating an example method of
communication in accordance with the techniques described above.
The method 900 may be performed, for example, by an access point
(e.g., the access point 110 or the access point 160 illustrated in
FIG. 1) operating on a shared communication medium. As an example,
the communication medium may include one or more time, frequency,
or space resources on an unlicensed radio frequency band shared
between LTE technology and Wi-Fi technology devices.
[0055] As shown, the access point may detect a connection failure
associated with mobility between a source access point and a target
access point sharing a communication medium (block 902). The access
point may be either the source or target access point. The access
point may then adapt, based on the detected connection failure, a
backoff threshold associated with contention-based access to the
communication medium (block 904) and contend for access to the
communication medium in accordance with the adapted backoff
threshold (block 906). It will be appreciated that the access point
may also (separately) adapt, based on the detected connection
failure, one or more handover parameters distinct from the backoff
threshold.
[0056] As discussed in more detail above, the adapting (block 904)
may comprise, for example, lowering the backoff threshold from a
first value to a second value in response to detecting the
connection failure.
[0057] The detecting (block 902) may utilize, for example,
communication between the source access point and the target access
point. Here, the detecting may further utilize MRO procedures. In
addition or as an alternative, the detecting (block 902) may
utilize communication between the access terminal and the source
access point, communication between the access terminal and the
target access point, or a combination thereof.
[0058] In some designs or scenarios, the access point may
coordinate the adapted backoff threshold between the source access
point and the target access point, via a backhaul connection, an
over-the-air connection, or an access terminal report.
[0059] In some designs or scenarios, the detecting (block 902) may
comprise classifying the detected connection failure and the
adapting (block 904) may comprise selectively adapting the backoff
threshold based on the classifying.
[0060] As an example, the adapting (block 904) may comprise
switching an LBT mode from a first detection mechanism having a
first backoff threshold to a second detection mechanism having a
second backoff threshold that is lower than the first backoff
threshold. For example, the first detection mechanism may
correspond to a CCA-ED mechanism and the second detection mechanism
may correspond to a CCA-PD mechanism.
[0061] The backoff threshold may be a RAT-specific threshold, with
the adapting (block 904) comprising, for example, setting a first
backoff threshold associated with a first RAT to a first value and
a second backoff threshold associated with a second RAT to a second
value that is different from the first value. The backoff threshold
may also be a Cell ID-specific threshold, with the adapting (block
904) comprising setting a first backoff threshold associated with a
first Cell ID to a first value and a second backoff threshold
associated with a second Cell ID to a second value that is
different from the first value.
[0062] It will be appreciated from the discussion above that the
connection failure may correspond, for example, to a handover
failure or an RLF.
[0063] For generality, the access point 110 and the access point
160 are shown in FIG. 1 only in relevant part as including the
contention manager 112 and the contention manager 162,
respectively. It will be appreciated, however, that the access
point 110 and the access point 160 may be configured in various
ways to provide or otherwise support the contention management
techniques discussed herein.
[0064] FIG. 10 is a device-level diagram illustrating example
components of the access point 110 and the access terminal 120 in
more detail. It will be appreciated that the access point 160 and
the access terminal 170 may be similarly configured, with the
example components of the access point 110 and the access terminal
120 being shown for illustration purposes only.
[0065] As shown, the access point 110 and the access terminal 120
may each generally include a wireless communication device
(represented by the communication devices 1030 and 1050) for
communicating with other wireless nodes via at least one designated
RAT. The communication devices 1030 and 1050 may be variously
configured for transmitting and encoding signals, and, conversely,
for receiving and decoding signals in accordance with the
designated RAT (e.g., messages, indications, information, pilots,
and so on).
[0066] The communication devices 1030 and 1050 may include, for
example, one or more transceivers, such as respective primary RAT
transceivers 1032 and 1052, and, in some designs, (optional)
co-located secondary RAT transceivers 1034 and 1054, respectively
(corresponding, for example, to the RAT employed by the second
system B 150, if different than the first system A 100). As used
herein, a "transceiver" may include a transmitter circuit, a
receiver circuit, or a combination thereof, but need not provide
both transmit and receive functionalities in all designs. For
example, a low functionality receiver circuit may be employed in
some designs to reduce costs when providing full communication is
not necessary (e.g., a radio chip or similar circuitry providing
low-level sniffing only). Further, as used herein, the term
"co-located" (e.g., radios, access points, transceivers, etc.) may
refer to one of various arrangements. For example, components that
are in the same housing; components that are hosted by the same
processor; components that are within a defined distance of one
another; and/or components that are connected via an interface
(e.g., an Ethernet switch) where the interface meets the latency
requirements of any required inter-component communication (e.g.,
messaging).
[0067] The access point 110 and the access terminal 120 may also
each generally include a communication controller (represented by
the communication controllers 1040 and 1060) for controlling
operation of their respective communication devices 1030 and 1050
(e.g., directing, modifying, enabling, disabling, etc.). The
communication controllers 1040 and 1060 may include one or more
processors 1042 and 1062, and one or more memories 1044 and 1064
coupled to the processors 1042 and 1062, respectively. The memories
1044 and 1064 may be configured to store data, instructions, or a
combination thereof, either as on-board cache memory, as separate
components, a combination, etc. The processors 1042 and 1062 and
the memories 1044 and 1064 may be standalone communication
components or may be part of the respective host system
functionality of the access point 110 and the access terminal
120.
[0068] It will be appreciated that the contention manager 112 (as
representative of the contention manager 112 and the contention
manger 162) may be implemented in different ways. In some designs,
some or all of the functionality associated therewith may be
implemented by or otherwise at the direction of at least one
processor (e.g., one or more of the processors 1042 and/or one or
more of the processors 1062), at least one memory (e.g., one or
more of the memories 1044 and/or one or more of the memories 1064),
at least one transceiver (e.g., one or more of the transceivers
1032 and 1034 and/or one or more of the transceivers 1052 and
1054), or a combination thereof. In other designs, some or all of
the functionality associated therewith may be implemented as a
series of interrelated functional modules.
[0069] Accordingly, it will be appreciated that the components in
FIG. 10 may be used to perform operations described above with
respect to FIGS. 1-9. For example, the access point 110 may, via
the processor 1042 and the memory 1044, detect a connection failure
associated with mobility between a source access point and a target
access point sharing a communication medium and adapt, based on the
detected connection failure, a backoff threshold associated with
contention-based access to the communication medium. The access
point 110 may, via the primary RAT transceiver 1032, configured to
contend for access to the communication medium in accordance with
the adapted backoff threshold.
[0070] FIG. 11 illustrates an example access point apparatus for
implementing the contention manager 112 and/or the contention
manager 162 represented as a series of interrelated functional
modules. In the illustrated example, the apparatus 1100 includes a
module for detecting 1102, a module for adapting 1104, and a module
for contending 1106.
[0071] The module for detecting 1102 may be configured to detect a
connection failure associated with mobility between a source access
point and a target access point sharing a communication medium. The
module for adapting 1104 may be configured to adapt, based on the
detected connection failure, a backoff threshold associated with
contention-based access to the communication medium. The module for
contending 1106 may be configured to contend for access to the
communication medium in accordance with the adapted backoff
threshold.
[0072] The functionality of the modules of FIG. 11 may be
implemented in various ways consistent with the teachings herein.
In some designs, the functionality of these modules may be
implemented as one or more electrical components. In some designs,
the functionality of these blocks may be implemented as a
processing system including one or more processor components. In
some designs, the functionality of these modules may be implemented
using, for example, at least a portion of one or more integrated
circuits (e.g., an ASIC). As discussed herein, an integrated
circuit may include a processor, software, other related
components, or some combination thereof. Thus, the functionality of
different modules may be implemented, for example, as different
subsets of an integrated circuit, as different subsets of a set of
software modules, or a combination thereof. Also, it will be
appreciated that a given subset (e.g., of an integrated circuit
and/or of a set of software modules) may provide at least a portion
of the functionality for more than one module.
[0073] In addition, the components and functions represented by
FIG. 11, as well as other components and functions described
herein, may be implemented using any suitable means. Such means
also may be implemented, at least in part, using corresponding
structure as taught herein. For example, the components described
above in conjunction with the "module for" components of FIG. 11
also may correspond to similarly designated "means for"
functionality. Thus, in some aspects one or more of such means may
be implemented using one or more of processor components,
integrated circuits, or other suitable structure as taught herein,
including as an algorithm. One skilled in the art will recognize in
this disclosure an algorithm represented in the prose described
above, as well in sequences of actions that may be represented by
pseudocode. For example, the components and functions represented
by FIG. 11 may include code for performing a LOAD operation, a
COMPARE operation, a RETURN operation, an IF-THEN-ELSE loop, and so
on.
[0074] It should be understood that any reference to an element
herein using a designation such as "first," "second," and so forth
does not generally limit the quantity or order of those elements.
Rather, these designations may be used herein as a convenient
method of distinguishing between two or more elements or instances
of an element. Thus, a reference to first and second elements does
not mean that only two elements may be employed there or that the
first element must precede the second element in some manner. Also,
unless stated otherwise a set of elements may comprise one or more
elements. In addition, terminology of the form "at least one of A,
B, or C" or "one or more of A, B, or C" or "at least one of the
group consisting of A, B, and C" used in the description or the
claims means "A or B or C or any combination of these elements."
For example, this terminology may include A, or B, or C, or A and
B, or A and C, or A and B and C, or 2A, or 2B, or 2C, and so
on.
[0075] In view of the descriptions and explanations above, one
skilled in the art will appreciate that the various illustrative
logical blocks, modules, circuits, and algorithm steps described in
connection with the aspects disclosed herein may be implemented as
electronic hardware, computer software, or combinations of both. To
clearly illustrate this interchangeability of hardware and
software, various illustrative components, blocks, modules,
circuits, and steps have been described above generally in terms of
their functionality. Whether such functionality is implemented as
hardware or software depends upon the particular application and
design constraints imposed on the overall system. Skilled artisans
may implement the described functionality in varying ways for each
particular application, but such implementation decisions should
not be interpreted as causing a departure from the scope of the
present disclosure.
[0076] Accordingly, it will be appreciated, for example, that an
apparatus or any component of an apparatus may be configured to (or
made operable to or adapted to) provide functionality as taught
herein. This may be achieved, for example: by manufacturing (e.g.,
fabricating) the apparatus or component so that it will provide the
functionality; by programming the apparatus or component so that it
will provide the functionality; or through the use of some other
suitable implementation technique. As one example, an integrated
circuit may be fabricated to provide the requisite functionality.
As another example, an integrated circuit may be fabricated to
support the requisite functionality and then configured (e.g., via
programming) to provide the requisite functionality. As yet another
example, a processor circuit may execute code to provide the
requisite functionality.
[0077] Moreover, the methods, sequences, and/or algorithms
described in connection with the aspects disclosed herein may be
embodied directly in hardware, in a software module executed by a
processor, or in a combination of the two. A software module may
reside in Random-Access Memory (RAM), flash memory, Read-only
Memory (ROM), Erasable Programmable Read-only Memory (EPROM),
Electrically Erasable Programmable Read-only Memory (EEPROM),
registers, hard disk, a removable disk, a CD-ROM, or any other form
of storage medium known in the art, transitory or non-transitory.
An exemplary storage medium is coupled to the processor such that
the processor can read information from, and write information to,
the storage medium. In the alternative, the storage medium may be
integral to the processor (e.g., cache memory).
[0078] Accordingly, it will also be appreciated, for example, that
certain aspects of the disclosure can include a transitory or
non-transitory computer-readable medium embodying a method for
communication.
[0079] While the foregoing disclosure shows various illustrative
aspects, it should be noted that various changes and modifications
may be made to the illustrated examples without departing from the
scope defined by the appended claims. The present disclosure is not
intended to be limited to the specifically illustrated examples
alone. For example, unless otherwise noted, the functions, steps,
and/or actions of the method claims in accordance with the aspects
of the disclosure described herein need not be performed in any
particular order. Furthermore, although certain aspects may be
described or claimed in the singular, the plural is contemplated
unless limitation to the singular is explicitly stated.
* * * * *